THREAD REMOVAL APPARATUS AND METHOD

Abstract: A web (W) of sheet material intended to form individual tagged packets has surplus portions of a thread (S) extending along its length removed while the web is being advanced. After severing one end of each unwanted thread portion with a rotary cutter (2), the severed end is lifted by a wiper (10), and the lifted end is held away from the web by suction means (20) while it is detached by shearing means (22). The suction means (20) then remove the detached thread portion.

Description: Thread removal apparatus and method This invention relates to the removal of portions of thread from a length of thread which is attached to a web of sheet material to extend along the length of the web. It is particularly concerned, although not necessarily exclusively so, with such a process as one stage in the production of infusion packets to which tags are attached by a thread. The use of such tagged packets is well known. Our earlier Patent Application EP 448325A, describes a process for producing the packets during which a series of spaced tags are attached to a length of thread and the thread and tags are attached to a web along its length. The procedure by which the tags and thread are assembled with the web is described in more detail in our earlier EP 489554A, to which reference can be made for further details. What is particularly significant in that assembly procedure in the present context is that it results in a continuous length of thread extending along the web in which only those portions that connect the tags to the web serve a useful purpose. The remaining portions can complicate subsequent stages in the process of producing the packets and can present an awkward appearance in the finished product. According to one aspect of the present invention there is provided means for removing portions of thread from a length of thread attached to a web, comprising means for severing one end of each said portion and means for holding said severed end spaced from the web while severing the other end of said portion to detach the portion from the web. Preferably, mechanical means are provided to lift the severed end of said thread portion away from the web, as for example a wiping or sweeping device. Conveniently suction means are employed to hold the severed end spaced from the web while the second end of said thread portion is severed, the suction means then being employed to remove the detached thread portion. According to another aspect of the invention, there is provided a method of removing portions of thread from a length of thread attached to a web while the web is being advanced, comprising severing one end of each portion at a first station in the path of the web advance and at a station downstream from said first station holding said severed end spaced from the web while severing the other end of said portion to detach the portion from the web. The invention will be further described by way of example with reference to the embodiments illustrated in the accompanying drawings, in which: Fig. 1 is a schematic illustration of the thread removing means according to the invention, Figs. 2a & 2b show the web, thread and tag assembly before and after the operation of the means of Fig . 1 , and Fig. 3 is a sectional view in a central vertical plane of a modified form of the thread removal means of Fig. 1. The illustrated apparatus is so arranged that a continuous web W of sheet material enters the means shown in Fig. 1 travelling in the direction A. After further process steps with which the present invention is concerned and which are described below, the web is eventually heat-sealed and severed at intervals along its length to provide a series of discrete packets, which may themselves take a generally conventional form, eg. as tea bags. As shown in Fig 2a, at this stage a thread S extends along the web W as it enters the apparatus. The thread is held in place by tags T . which are spaced along the web to provide one tag to each of the packets eventually formed from the web. Tacking heat seals (not shown) attach the tags releasably to the web and adhesive seals A secure them to the thread. Between the adhesive connections of the thread to the web and the tag of each packet the thread is gathered, eg. in a loop , and this excess length is held secure under the tag by the attachment of the tags to the webs. The portions of the thread S, from its connection A to a tag T to close to the point at which it runs under the following tag, serve no purpose in the finished packets. While they remain in place they complicate the formation of the transverse seals that define the individual packets and the severing of those packets from each other. It would be desirable to remove these portions first but if the web, thread and tags are assembled together in a continuous process, such as that described in EP 489554, this should be done in a way which does not slow that process. The apparatus now to be described thus operates on the moving assembly of web, thread and tags. As it enters the illustrated apparatus, the web W passes between a cutter plate 2 mounted on a rotary shaft 4 and a counter-rotating anvil 6. The equispaced cutting tips 2' on the periphery of the cutter plate 2 act on the thread S immediately ahead of each tag T, severing the thread at these points, which represent one end of each portion of thread to be removed. The web is also cut by the cutting tips 2a but this is not significant because the cuts are co-incident with the ends of the packets eventually. The web then passes under a rotary wiper 10 from which at least one elastomeric finger 12 projects radially. The wiper is rotated by a belt drive 14 in the arrowed direction B so that the wiper finger 12 moves in the same direction as the web over the lowest part of its rotary path but at a considerably faster speed. In this lowest portion of its path the finger 12 comes into contact with the thread S towards the rear of the tag T. As it bears on the tag and thread, the finger 12 sweeps the severed end of the thread upwards and forwards . The displacement of the loose thread end by the wiper finger 12 is reinforced by a suction nozzle 20 which has openings (not shown) both in its end facing the rotary wiper 10 and on its underside where it passes over a pair of rotating cutter discs 22 acting as shears. At their nip the shearing edges of the disc move in the same direction as the web but at a faster speed. The web passes under the discs but the lifted thread is severed by them, close to its attachment to the web. The unwanted thread portion is thereby completely detached and the suction force removes it, through the nozzle 20, to a waste collection location (not shown) to ensure that it does not interfere with the subsequent packet production process. The assembly of the web thread and tags is now as shown in Fig. 2b. The movements of the cutter plate 2 and the rotary wiper 10 are synchronised with the web movement to register them with the required locations on the thread for their action, but this is not necessary for the cutter discs. Alternative cutting means can be provided, in particular in place of the shear discs slitting means or crush cutting means can be employed. Fig. 3 illustrates another embodiment of the invention with a number of detail features that can be employed in the embodiment of Fig. 1 also. Parts that are essentially the same as those already described with reference to Fig. 1 are indicated by the same reference numbers with the suffix "a". The web, with its thread and tags, is not shown in Fig. 3 but is identical to that described with reference to Fig. 2a. The embodiment of Fig. 3 also has a cutter plate 2a on shaft 4a acting against counter-rotating anvil 6a, rotary wiper 10a with finger 12a, rotating cutter discs 22a and suction nozzle 20a. In this case, the thread and tags are located on the underface of the web (not shown) so* that the cutter plate 2a, wiper 10a, cutter discs 22a and suction nozzle 20a are disposed below the web path. The cutter plate rotates in a void in a stationary guide cylinder 32 over which the web is led and further along the web path a backing plate 34 extends over the rotary wiper 12a and entry slot 36 of the suction nozzle as a support and location for the web, assisting the action of the wiper and the cutter discs 22a. The leading end of the slot 36 has flared faces 38 widening the leading end of the slot to ensure that the severed ends of the thread are drawn into the slot before the unwanted portions are cut free by the discs. The anvil 6a is journalled in a mounting 42 that can be lifted on gas struts (not shown) about a pivot axis parallel to the plane of Fig. 3 but behind the anvil to assist threading the web past the slot 36 and the backing plate 34 swings about the pivot 40 for the same purpose. A link 44 connects the backing plate 34 to the mounting 42 so that it is lifted simultaneously with the anvil. In the illustrated examples, the thread is not directly connected to the web but in use a permanent connection will be required between each remaining thread length and the web at the end of the thread length remote from its attachment A to the tag. This further connection can be provided subsequently by heat-sealing means or by adhesive. It is also possible to make the connections before removing the unwanted thread lengths, particularly if adhesive is used for this.

Claims: CLAIMS 1. Means for removing portions of thread from a length of thread attached to a web, comprising means (2) for severing one end of each said portion and means (20,22) for holding said severed end spaced from the web while severing the other end of said portion to detach the portion from the web. 2. Thread removal means according to claim 1 wherein said holding means comprises suction means (20) arranged to draw the severed end away from the web. 3. Thread removal means according to claim 2 wherein said suction means (20) are also arranged to remove the detached thread portion. 4. Thread removal means according to any one of claims 1 to 3 wherein means (12) are provided to displace said severed end away from the web, prior to the action of said holding means. 5. Thread removal means according to any one of the preceding claims comprising a shearing means (22) arranged in a stationary position relative to the path of advance of the web for said detachment of the thread portion. 6. Thread removal means according to any one of the preceding claims wherein the means (2,22) for severing the respective ends of the thread portions are spaced from each other along an advance path of the web and said severing means for said one end of the thread portions comprises counter-rotating cutting and anvil members (2,6) between which said thread is pinched, said members being arranged to rotate in the direction of advance of the web. 7. Apparatus according to any one of the preceding claims wherein a fixed support (34) is provided for one face of the web and the displacement means (12) and/or suction means (20) and/or detaching means (22) are disposed along the extent of said support means over the opposite face of the web. 8. A method of removing portions of thread from a length of thread attached to a web while the web is being advanced, comprising severing one end of each portion at a first station in the path of the web advance and at a station downstream from said first station holding said severed end spaced from the web while severing the other end of said portion to detach the portion from the web. 9. A method according to claim 8 wherein the severed end of the thread is held spaced from the web by suction. 10. A method according to claim 8 or claim 9 wherein said thread portion is removed by suction after its detachment from the web. 11. A method according to any one of claims 8 to 10 wherein said one end of each thread portion is severed by cutting means (2) advancing with the web at substantially the same velocity during the severing operation. 12. A method according to any one of claims 8 to 11 wherein the thread portions are detached by a shearing action employing shearing means (22) which have active cutting regions moving faster than the web in its direction of advance.

Inventors: BAILEY THOMAS WILLIAM, BAILEY, THOMAS, WILLIAM
Applicants: UNILEVER NV, UNILEVER PLC, UNILEVER N.V.
Application year: 1994
Main classification: B65B29
IPC codes: B65B29